1. Field of the Invention
The invention relates to a catheter for aspirating, fragmenting and removing removable materials from hollow bodies, in particular thrombi and emboli from blood vessels.
2. Description of Related Art
Such catheters are used in particular for the treatment of occlusive arterial diseases by aspiration, fragmentation and removal of emboli and thrombi. They are introduced into the artery or vein and advanced, preferably with X-ray monitoring, up to the narrowed or blocked area that is to be treated. A fragmentation tool drivable in a rotary manner by means of a rotary drive, and a working head, are arranged at their front or distal end.
In the case of these catheters, a distinction should be made as a rule on the basis of two different fields of use:
A) Atherectomy
This is the removal of, as a rule, hard deposits that have adhered to the vessel walls over many years.
B) Thrombectomy
This is the removal of fresh blood clots that accumulate at bottlenecks and lead to blockage of the blood vessels (emboli).
A rotational catheter disclosed, for example, in European Patent No. EP 0 267 539 B1 and intended for atherectomy has, as a cutting tool, a substantially ellipsoidal cutter whose surface is provided with abrasive material and that is driven via a flexible drive shaft by a rotary drive arranged at the proximal end of the catheter at a speed of up to 160,000 rpm. The cutter is connected to the flexible drive shaft. The drive shaft runs in a tubular sheath serving as a catheter tube. A guide wire, which is introduced into a blood vessel before the introduction of the catheter, is advanced to the area to be treated or slightly beyond, and serves as a guide for the cutter and the drive shaft, extends through the drive shaft.
In the case of these known rotational catheters, the risk that the vessel wall will be injured and in certain circumstances even perforated, particularly in pronounced curves of the blood vessel, cannot be ruled out.
A further rotational catheter disclosed in U.S. Pat. No. 5,571,122 has a cutting tool with a multiplicity of peeling knives extending in the axial direction and driven at a speed of about 800 rpm. By axial compression of the cutting tool, the peeling knives can be caused to bulge radially outward and the external diameter of the cutting tool is thus increased. In the case of this catheter, there is the risk that, particularly as a result of the relatively slow circumferential speed, the peeling knives may pull, drag or jam against the vessel wall, with the result that the blood vessels react dramatically in that they contract and thus prevent further intervention.
U.S. Pat. No. 5,226,909 discloses another atherectomy catheter that has, on its working head, a sleeve-like or helical cutting element drivable by a rotary drive and/or displaceable in the axial direction. The opening of the working head is pressed against the deposits adhering to the vessel wall by means of a lateral inflatable balloon. These deposits are then comminuted by rotation or axial advance of the cutting element and are collected in a chamber. The chamber must then be emptied from time to time by withdrawing the catheter. Continuous removal of comminuted deposited material is not envisaged.
PCT Patent Publication No. WO 96/29941 A1 describes a rotational catheter for atherectomy, whose working head includes a stationary stator, connected to a tube, and a rotor. The rotor is rotatable relative to the stator by means of a high-speed transport/drive screw. Both the stator and the rotor have, at their circumference, windows that can be caused to coincide. As a result of shearing between a cutting edge on the rotor and an opposite cutting edge on the openings of the stator, comminution of the parts projecting into or sucked into the openings is effected. The rotor may surround the stator on the outside (“outer rotor”) or may be arranged in the interior of the stator (“inner rotor”).
Catheters having inner and outer rotors with cutting edges that operate around the catheter axis have the disadvantage that they stir up blood and occlusion material, so that the blood flow from proximal to distal may wash away particles that may again produce blockages and blood flow problems in other areas of the blood circulation, particularly in small blood vessels.
Further documents relating to the prior art include EP and PCT Publications, EP Patents, and US Patents having the following numbers: EP 0 310 285 A2; EP 0 448 859 A2; EP 0 669 106 A2; EP 0 680 730 A2; EP 0 669 106 B1; EP 0 739 603 A1; WO 02/49690 A2; U.S. Pat. Nos. 4,857,046 and 5,100,426.
Rotational catheters known to date and comprising revolving knife-like elements or cutters require a relatively powerful rotary drive, which in turn necessitates a more powerful, rotationally-more-rigid catheter tube for compensating the moment of reaction that arises during cutting of particles, in order that the catheter tube does not rotate about the longitudinal axis. However, a stronger or rotationally-more-rigid tube is inevitably less flexible, with the result that the catheter is in certain circumstances disadvantageous in the curves of blood vessels.
It is the object of the invention to provide a catheter, in particular for thrombectomy, that has no externally revolving cutting knife, cutter or the like, operates in an atraumatic manner and can aspirate and fragment thrombi and emboli in the blood vessel and transport them through the catheter tube continuously out of the vessel.
It is therefore intended to achieve a reduction in components and to minimise the risk of injury to walls of blood vessels. The advantages of known systems, in particular those of the system according to PCT Publication No. WO 96/29941 A1 are however to be retained.